This invention relates to a slatted blind comprising vertically disposed and laterally movable slats which are pivotable about their longitudinal axes.
In particular, the invention concerns a slatted blind of the kind in which each slot is mounted at a top end thereof on pivot means carried by a respective guide carriage movable along a support rail, at least one of the guide carriages carrying a nut which is rotatably and axially immovably mounted on the carriage and is engaged on a rotatable threaded operating rod extending longitudinally of the support rail, a first gear ring rotatable with said nut being meshed with a second gear ring disposed on said pivot means, rotation of said second gear ring in response to rotation of the operating rod being transmitted to said slat through a slip clutch which is operative to rotate the slat about its longitudinal axis to a limiting position and then to slip to cause displacement of the guide carriage along the support rail.
A blind of this kind is disclosed in German Auslegeschrift 1659557. In this known blind, the nut is formed both with internal threading co-operating with the operating shaft and with external threading which constitutes the first gear ring.
In the form of the known blind, each guide carriage is provided with a nut engaged on the operating rod and all the guide carriages are simultaneously displaced along the support rail. In another form only a single traction carriage is is provided with a nut engaged on the operating rod, only this traction carriage being displaced along the support rail by the operating rod, the remaining carriage being entrained by the traction carriage at predetermined spacings. Spacers situated between the pivot means of adjacent slats are provided to limit the relative slidability of the slats.
The known slatted blind suffers from the disadvantage of having a relatively complicated construction. For example, a guide carriage of the known blind comprises 13 or even more individual components. This leads to high manufacturing and assembling costs and more particularly to a corresponding proneness to operating defects. However, manufacturing costs and operational reliability are particularly important features for articles such as slatted blinds which are operated frequently in use. Operation is moreover usually performed by lay people who frequently do not exercise sufficient care. A slatted blind should therefore have adequate operational reliability and a long service life even under such conditions.
Furthermore, the rate of wear of the known blind is unsatisfactory. An important seat of wear is situated in the slip clutch which, in the known blind, is located between the second gear ring and a bottom end of a pivot shaft constituting the pivot means. In this arrangement, the second gear ring is constructed as an externally geared sleeve which extends a taper member provided on the bottom of the pivot shaft. A taper bush is retained in the gear ring sleeve so as to be non-rotatable but axially slidable and is biased into engagement with the taper member by a spring.
It is therefore an object of the invention to improve the known blind so that the manufacturing and assembly costs as well as the storage costs for replacement parts can be substantially reduced and that moreover the operational reliability is improved and the rate of wear is reduced.